Method for producing stencils



Patented Jan. 26, 1943 METHOD FOR PRODUCING STENCILS V Ernst Buri, Donaueschingen, Germany, assignor to Hans Fretz, Zurich, Switzerland No Drawing.

Application February 17, 1940,

Serial No. 319,47 9. In Germany March 7, 1939 4 Claims.

My invention relates to a method of producing stencils, for instance stencil sheets perforated by characters, drawings or the like as they are in use for multiplicators or other office machines or for textile purposes.

Hitherto such stencils for example of japan fibre-paper coated with derivatives of cellulose, protein, wax or the like have been provided with characters or drawings either by photo-mechanical methods or by way of engraving or stamping. These methods require much time; especially if a plurality of equal stencils are to be produced every single stencil must be traced, brushed or developed photomechanically.

In the method of my invention the original stencil is transferred to the derivative stencil in a simplified manner by way of a caustic process. The original stencil may be for instance a photomechanically perforated sheet or layer of gelatine or metal or of any other suitable caustic resisting material.

In the usual etching methods in which liquid caustics are employed the derivative stencil for instance of a cellulose derivate is liable to be worn away by the liquid caustic whereby the fine strokes of the characters or drawings are enlarged or destroyed.

According to my invention this drawback is overcome by making vapors of suitable solvents instead of the liquid solvents themselves to act on the material of the derivative stencils.

The method may for example be performed in the following manner. A sheet or layer of cellulose adapted for a stencil is placed in close contact with the original or master stencil which, for example, consists of gelatine or metal or of any other suitable material. A fluid absorbing sheet for example a blotting-paper or a plate of clay or the like saturated with a solvent for cellulose is then placed on the original stencil and the whole pressed together. In order to obtain a uniform action of the vapors of the solvent the pressure will preferably be applied by means of a small press worked by manual power, whereat the pressing action may be repeated until all lines and strokes of the original stencil are visible on the back of the derivative stencil. The derivative stencil thus prepared may be detached from the original stencil by means of water and is then ready for use in multiplicators or the like.

Instead of applying an original stencil in the form of a separate perforated sheet, the original stencil may be made as a coat or layer of a material resisting to a solvent adhering to the sheet of cellulose, whereafter the coat or layer will be perforated in any suitable manner by characters or drawings which are then transferred to the sheet of cellulose by applying vapors of a solvent as described above.

The original stencil may be made as a layer of caustic resisting material adhering to silk gauze or to any other thin fabric of a fine hard spun fibre.

I claim:

1. The method of producing stencils of cellulose, which consists in bringing a sheet of cellulose into close contact with a master stencil consisting of a layer of a material which is insoluble in a predetermined solvent, and applying vapors of said solvent to said master stencil and, through the perforations therein, to said sheet of cellulose in such a manner that an etching action on the portions of the sheet of cellulose corresponding to the perforations of said master stencil is produced exclusively by the vapors penetrating through said perforations.

2. The method of producing stencils of cellulose, which consists in perforating a sheet of material which is insoluble in a predetermined solvent to form a master stencil, bringing a sheet of cellulose into close contact with said perforated master stencil, and applying vapors of said solvent to said master stencil and, through the perforations therein, to said sheet of cellulose in such a manner that an etching action on the portions of the sheet of cellulose corresponding to the perforations of said master stencil is produced exclusively by the vapors penetrating through said perforations.

3. The method of producing stencils of cellulose, which consists in coating a sheet of cellulose with a layer of material which is insoluble in a solvent for cellulose, perforating said layer of solvent resisting material, and applying vapors of said cellulose solvent to said perforated layer and, through the perforations therein, the said sheet of cellulose in such a manner that an etchmg action on the portions of the sheet of cellulose corresponding to the perforations of said layer is produced exclusively by the vapors penetrating through said perforations.

4. The method of producing stencils of cellulose, which consists in bringing a sheet of cellulose into close contact with a perforated layer of solvent resisting material, placing a fluid absorbing sheet saturated with a solvent for cellulose on the layer of solvent resisting material, and pressing said sheets and interposed perforated layer together in such a manner that an etching action on the portions of the sheet of cellulose corresponding to the perforations of the layer of solvent resisting material is produced exclusively by the vapors penetrating through said perforations.

ERNST BURI. 

